Collision-induced dissociation (CID) of dipeptide sulfinyl radical ion
Cysteine sulfinyl radical is an important radical species that has been observed in biological enzyme systems. Our group has managed to generate site-specific cysteine sulfinyl radicals via helium low temperature plasma (LTP) in gas phase and study them via mass spectrometry (MS). Dipeptide sulfinyl radicals serve as a great platform for understanding the effect of amino acid properties (basic, acidic, neutral) as well as the location of sulfinyl radical on the fragmentation behavior of the radical species. N-terminal acetylation is also carried out since proton mobility can significantly affect the dissociation of radical species, which helps to gain a better insight into the competition between charge vs. radical directed fragmentation. Dipeptide sulfinyl radical anions are also examined, and the one with acidic residue is shown to give a better yield of glycyl radical anion in CID, which is an important radical intermediate but has been rarely studied in the negative mode due to the limited ways of generation. When sodium ion is introduced as charge carrier, it can greatly enhance the formation of glycyl radical in both positive and negative mode.
Xia, Purdue University.
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